374
J. Agric. Food Chem. 2004, 52, 374−379
Far-Infrared Radiation Increases the Antioxidant Properties of
Rice Hull Extract in Cooked Turkey Meat
K. C. NAM,† JEONG-HAN KIM,§ DONG U. AHN,†
AND
SEUNG-CHEOL LEE*,§
Department of Animal Science, Iowa State University, Ames, Iowa 50011-3150, and Department of
Food Science and Biotechnology, Kyungnam University, Masan 631-701, Korea
To determine the antioxidant effects of rice hull extract exposed to far-infrared radiation, the added
extracts were compared with sesamol in cooked turkey breast. Rice hull extract showed antioxidant
properties in cooked turkey breast by reducing lipid oxidation and volatile aldehydes. Far-infrared
radiation increased significantly the antioxidant activities of rice hull extracts. Rice hull extract irradiated
by far-infrared (FRH) had lower TBARS values and fewer volatile aldehydes (hexanal, pentanal, and
propanal) than a non-irradiated extract (IRH) during the 3 days of aerobic storage. Addition of FRH
at 0.2% (w/w) in turkey meat could reduce the amounts of volatile hexanal to 18-47% of the control
during the storage. However, the antioxidant activities of rice hull extracts did not last as long as
those of pure sesamol due to the relatively low concentration of phenolics, and the extracts had
some peculiar odor. Addition of rice hull extracts also increased both a and b values of the samples
due to its brown intensity.
KEYWORDS: Rice hull extract; far-infrared; turkey breast; antioxidant activity
INTRODUCTION
Antioxidant activities have been reported from various plant
sources, such as grape seeds, pine bark, olive rape, rosemary,
and cocoa byproduct (1-3). Some parts of plants may play an
important role in chemical protection from oxidative damage
because they possess endogenous antioxidant phenolic compounds, and the antioxidant activity of a certain fraction is higher
than that of others (4, 5).
Rice hulls also contain an antioxidant defense system to
protect rice seed against oxidative stress (6). There have been
a few reports on the antioxidant activities of rice hull extracts.
Ramarathnam et al. (7) identified isovitexin as a natural
component in white rice hull, which showed strong antioxidants
inhibiting lipid peroxidation. Wu et al. (8) reported that wild
rice kernels contained 2.1-2.4% phytic acid, a strong chelating
agent showing antioxidant activity. Asamarai et al. (9) identified
a few phenolic compounds, such as anisole, vanillin, and
syringaldehyde, in wild rice hull extract. In our previous study
(10), methanolic extracts of rice hull contained several phenolic
compounds such as o-methoxycinnamic acid, 4,7-dihydroxybenzoic acid, and p-coumaric acid, which are known to have
antioxidant effects. Thus, rice hull should receive greater
attention as an economical natural antioxidant source.
Many natural antioxidant compounds, however, exist naturally
bound to high molecular weight compounds or constitute part
of the repeating subunits of high molecular weight polymers
* Corresponding author (telephone +82-55-249-2684; fax +82-55-2492995; e-mail sclee@kyungnam.ac.kr).
† Iowa State University.
§ Kyungnam University.
(11). Far-infrared (FIR) radiation was thought to liberate and
activate low molecular weight natural antioxidant compounds,
because it heats materials without degrading the constitutive
molecules of the surface and contributes to an even transfer of
heat to the center of the materials (12). We found antioxidant
activities and phenolic contents increased after exposure of rice
hulls to FIR radiation (13).
Precooked meats are easily susceptible to lipid oxidation and
production of off-odor volatiles, and the use of antioxidants is
commonly required to retard the oxidative quality deterioration
during the meats’ shelf life. The need for natural antioxidants
is increasing in the food and meat industries to meet the
requirements of consumers demanding safer and natural antioxidants. Although a few natural extracts with antioxidant
activities are widely used as safe antioxidants, they are not as
effective as the synthetic antioxidants and the manufacturing
cost is high (14). Therefore, the antioxidant properties of rice
hull extract treated by FIR can be evaluated in the poultry meat
system, which is susceptible to lipid oxidation due to a relatively
high proportion of polyunsaturated fatty acids.
The objectives of this study were to determine the effects of
rice hull extract irradiated by FIR on lipid oxidation, production
of volatile compounds, and color changes of cooked turkey
breast during refrigerated storage.
MATERIALS AND METHODS
Preparation of Rice Hull Extracts. Rice hulls from a rice cultivar
(Oriza satiVa L. Japonica) were purchased from a local pounding plant
(Kimcheon, South Korea). The rice hulls were ground in a mill to pass
through a 48-mesh sieve. For FIR irradiation, rice hulls (5.0 g) in a
10.1021/jf035103q CCC: $27.50 © 2004 American Chemical Society
Published on Web 01/03/2004
Rice Hull Extract on Turkey Meat Quality
wooden box (50 cm × 40 cm × 40 cm) were irradiated for 120 min
with a FIR lamp (35 × 10 cm, 100 V, maximum 300 W, Hakko Electric
Machine Works Co., Ltd., Nagano, Japan), generating heat in the
wavelength range of 2-14 µm within the spectrum. The sample-holding
tray in the middle of the treatment box faced the FIR heater in a parallel
position, and the distance between the rice hull sample and the heater
was 20 cm. Each 300 g portion of rice hulls irradiated by FIR or not
was extracted with 1.5 L of methanol overnight at room temperature.
The extract was filtered through a Whatman nylon membrane filter
(0.2 µm), and then the filtrate was evaporated to dryness under reduced
pressure on a rotary evaporator at 40 °C. The extract was stored at 4
°C with nitrogen filling and dissolved with ethanol before use.
Consequently, two types of rice hull extracts were prepared, an intact
rice hull extract not irradiated by FIR (IRH) and an irradiated rice hull
extract (FRH).
Sampling of Turkey Breast Patties. Turkey breast muscles
(Pectoralis major) from 16 different turkeys were divided into four
groups and separately ground through a 3 mm plate. Six different turkey
patty treatments were prepared using sesamol and rice hull extracts
prepared as above: (1) control, no additive; (2) sesamol (3,4methylenedioxyphenol; Sigma, St. Louis, MO), 0.01% added; (3) IRH,
0.1% added; (4) IRH, 0.2% added; (5) FRH, 0.1% added; and (6) FRH,
0.2% added. Each additive was added to the ground turkey breast and
mixed for 3 min in a bowl mixer (model KSM 90; KitchenAid Inc.,
St. Joseph, MI). Rice hull extracts were dissolved in ethanol at the
concentration of 200 mg/mL before addition, and the same amounts
of ethanol were added to all treatments to minimize the effect of the
solvent. The mixed meats were ground again through a 3 mm plate to
ensure even distribution of the added additives. Turkey breast patties
were prepared using ∼100 g of meat and were cooked in a convection
oven to an internal temperature of 70 °C. After cooking, turkey patties
were vacuum-packaged and chilled in running cold water for 10 min.
Then the patties were individually transferred into oxygen-permeable
bags (polyethylene, 4 × 6, 2 mil, Associated Bag Co., Milwaukee,
WI). The aerobically packaged samples were stored at 4 °C, and lipid
oxidation, color, and volatile compounds of the samples were determined at 0, 1, and 3 days.
2-Thiobarbituric Acid-Reactive Substances (TBARS) Values.
Lipid oxidation was determined by measuring TBARS content (15).
Minced sample (5 g) was placed in a 50 mL test tube and homogenized
with 15 mL of deionized distilled water (DDW) using a Brinkman
Polytron (type PT 10/35, Brinkman Instrument Inc., Westbury, NY)
for 15 s at high speed. The meat homogenate (1 mL) was transferred
to a disposable test tube (13 × 100 mm), and butylated hydroxytoluene
(7.2%, 50 µL) and thiobarbituric acid/trichloroacetic acid [20 mM TBA
and 15% (w/v) TCA] solution (2 mL) were added. The sample was
mixed using a vortex and then incubated in a 90 °C water bath for 15
min to develop color. After cooling for 10 min in cold water, the
samples were vortexed and centrifuged at 3000g for 15 min at 5 °C.
The absorbance of the resulting upper layer was read at 531 nm against
a blank prepared with 1 mL of DDW and 2 mL of TBA/TCA solution.
The amounts of TBARS were expressed as milligrams of malonedialdehyde (MDA) per kilogram of meat.
Color Measurement. CIE color values were measured on the surface
of samples using a LabScan colorimeter (Hunter Associated Laboratories, Inc., Reston, VA) that had been calibrated against black and
white reference tiles covered with the same packaging materials as used
for the samples. The CIE L (lightness), a (redness), and b (yellowness)
values were obtained using an illuminant A (light source). Area view
and port size were 0.25 and 0.40 in., respectively. The values from
four random locations of upper and bottom surfaces were obtained,
averaged, and used for statistical analysis.
Analysis of Volatile Compounds. A dynamic headspace analysis
was performed using a Solatek 72 multimatrix vial autosampler and a
purge and trap concentrator 3000 (Tekmar-Dohrmann, Cincinnati, OH)
connected to a gas chromatograph-mass spectrometer (GC-MS,
Hewlett-Packard Co., Wilmington, DE) according to the method of
Ahn et al. (16). Minced sample (1 g) was placed in a 40 mL sample
vial, and the vials were then flushed with helium gas (40 psi) for 3 s
and capped airtight with a Teflon fluorocarbon resin/silicone septum
(I-Chem Co., New Castle, DE). The maximum waiting time of a sample
J. Agric. Food Chem., Vol. 52, No. 2, 2004
375
Table 1. TBARS Values of Cooked Turkey Breast Meat with the
Addition of Intact Rice Hull Extract (IRH) and Far-Infrared-Radiated
Rice Hull Extract (FRH) during Refrigerated Storagea
mg of MDA/kg of meat
storage
time (days)
control
sesamol
0.01%
0
1
3
SEM
1.35az
3.35ay
6.56ax
0.07
0.52dz
0.96ey
2.21ex
0.05
IRH
FRH
0.1%
0.2%
0.1%
0.2%
SEM
0.94bz
2.43by
6.01bx
0.02
0.78cz
1.86cy
4.50cx
0.10
0.76cz
1.92cy
4.16dx
0.10
0.71cz
1.38dy
2.04ex
0.07
0.04
0.07
0.10
a Different letters (a−d) within a row are significantly different (P < 0.05), n )
4. Different letters within a column (x−z) with the same meat are significantly different
(P < 0.05).
in a refrigerated (4 °C) loading tray was 2 h or less to minimize
oxidative changes during the waiting period before the start of the
analysis. The meat sample was purged with helium gas (40 mL/min)
for 14 min at 40 °C. Volatiles were trapped using a Tenax/charcoal/
silica column (Tekmar-Dohrmann) and desorbed for 2 min at 225 °C,
focused in a cryofocusing module (-80° C), and then thermally
desorbed into a column for 60 s at 225 °C.
An HP-624 column (7.5 m, 0.25 mm i.d., 1.4 µm nominal), an HP-1
column (52.5 m, 0.25 mm i.d., 0.25 µm nominal; Hewlett-Packard Co.,
Wilmington, DE), and an HP-Wax column (7.5 m, 0.250 mm i.d., 0.25
µm nominal) were connected using zero dead-volume column connectors (J&W Scientific, Folsom, CA). Ramped oven temperature was used
to improve volatile separation. The initial oven temperature of 0 °C
was held for 1.5 min. After that, the oven temperature was increased
to 15 °C at 2.5 °C/min, increased to 45 °C at 5 °C/min, increased to
110 °C at 20 °C/min, and then increased to 170 °C at 10 °C/min and
held for 2.25 min at that temperature. A constant column pressure at
20.5 psi was maintained. The ionization potential of the mass selective
detector (model 5973; Hewlett-Packard Co.) was 70 eV, and the scan
range was m/z 19.1-350. Identification of volatiles was achieved by
comparing mass spectral data of samples with those of the Wiley library
(Hewlett-Packard Co.). Standards, when available, were used to confirm
the identification by the mass selective detector. The area of each peak
was integrated using ChemStation software (Hewlett-Packard Co.), and
the total peak area (total ion counts × 104) was reported as an indicator
of volatiles generated from the meat samples.
Statistical Analysis. The experimental design was to determine the
effects of additives and storage time on lipid oxidation, volatile
compounds, and color of the cooked samples using four replications.
Analysis of variance was conducted according to the procedure of the
General Linear Model using SAS software (17). Student-NewmanKeul’s multiple-range tests were used to compare the significant
differences of the mean values of treatments (P < 0.05). Mean values
and standard error of the means (SEM) are reported.
RESULTS AND DISCUSSION
TBARS Values in Cooked Turkey Meat. Rice hull extracts
showed significant antioxidant activity in precooked turkey
breast (Table 1). At the beginning of storage, both IRH and
FRH had antioxidant effects with lower TBARS values compared with the control, but their TBARS were higher than that
of the sesamol despite the different concentrations. With
lengthening storage, the overall lipid oxidation was drastically
accelerated due to the denatured structure of the muscles by
cooking and aerobic storage conditions.
The effects of FIR radiation and added concentration were
more distinctive in stored samples. When IRH and FHE were
added at the concentration of 0.2% in meat, the TBARS values
decreased to 75 and 31% of the control, respectively, at 3 days.
FIR radiation of rice hull extract elevated the antioxidant activity
by >2 times in precooked turkey meat at 3 days. On the other
376
J. Agric. Food Chem., Vol. 52, No. 2, 2004
Nam et al.
et al. (18) reported that the antioxidant activity of vegetable
extracts is related to their polyphenol content and structure. In
our previous study (13), FIR radiation for 120 min onto rice
hull increased total phenolic contents from 0.12 to 0.18 mM,
DPPH radical scavenging activity from 47.74 to 82.98%, and
inhibition of lipid peroxidation from 41.07 to 48.44%, respectively. The GC-MS analysis results indicated that FIR radiation
on rice hull increased many phenolic compounds and generated
3-vinyl-1-oxybenzene, p-hydroxybenzaldehyde, vanillin, phydroxybenzoic acid, 4,7-dihydroxyvanillic acid, and isoferulic
acid. From this point, FIR radiation could increase antioxidant
properties of rice hull extract; thus, FRH is better able to keep
TBARS values in cooked meat lower than IRH.
Color Changes by Rice Hull Extracts. Due to the characteristic brown color of rice hull extracts, both a and b values
drastically increased in cooked turkey breast and the L value
had a tendency to decrease (Table 2). This should be a
detrimental effect of added rice hull extracts in the aspect of
color of turkey breast because consumers usually expect the
color of cooked poultry breast meat to be white. To increase
the availability of rice hull extracts as a food additive, a way to
decrease the color intensity is needed by concentrating more
antioxidant compounds and/or excluding the pigments portion.
At 3 days of refrigerated storage, the a and b values were
higher in FRH-added samples than in IRH-added ones because
the browning intensity of FRH rose during the irradiation by
FIR. The sesamol-added treatment did not show any great color
change at the beginning of storage, but the a values were
maintained during the aerobic storage, whereas those of the
control declined by pigment oxidation. This pigment-stabilizing
Table 2. Color Values of Cooked Turkey Breast Meat with the
Addition of Intact Rice Hull Extract (IRH) and Far-Infrared-Radiated
Rice Hull Extract (FRH) during Refrigerated Storagea
storage
time
(days)
sesamol
control
0.01%
IRH
0.1%
FRH
0.2%
0
1
3
SEM
81.65ax
82.47ax
80.77ay
0.30
82.04ax
81.60bxy
80.22ay
0.22
L Value
81.95ax
80.67bx
80.71bcy 80.24bcx
80.52aby 79.28cy
0.20
0.26
0
1
3
SEM
6.65cx
5.36dy
4.08fz
0.09
6.97bcx
6.83bx
6.07by
0.10
a Value
7.31bx
8.18ax
6.31cy
7.16ay
4.95ez
5.41dz
0.07
0.14
0
1
3
SEM
16.91dy
17.39dx
17.84ex
0.17
17.58dx
17.70dx
16.89fy
0.14
b Value
19.32c
21.43ax
19.18c
20.47ay
19.07d
19.86by
0.16
0.29
0.1%
0.2%
SEM
81.86ax
80.65bcy
79.80bcz
0.24
79.95c
80.58c
79.82bc
0.25
0.24
0.24
0.24
6.96bcx
6.80bx
5.79cy
0.86
8.04ax
6.92by
6.50az
0.13
0.15
0.08
0.07
21.91ax
20.83ay
20.55ay
0.19
0.24
0.17
0.11
20.19bx
19.95bx
19.41cy
0.11
a Different letters (a−d) within a row are significantly different (P < 0.05), n )
4. Different letters (x−z) within a column with the same color value are significantly
different (P < 0.05).
hand, the antioxidant effects of IRH did not last as FRH at 3
days and the TBARS of 0.1% IRH were almost the same as
the control.
The TBARS value of FRH was very dependent on the level
of added amounts, and 0.1% FRH was almost half of the 0.2%
FRH for turkey meat stored for 3 days. The TBARS of 0.2%
FRH treatment was the same as that of the 0.01% sesamol. Foti
Table 3. Volatiles Profile of Cooked Turkey Breast Meat with the the Addition of Intact Rice Hull Extract (IRH) and Far-Infrared-Radiated Rice Hull
Extract (FRH) at 0 Daysa
total ion counts × 104
sesamol
compound
hydrocarbons
1,1′-oxybisethane
1-heptene
2-octene
nonane
octane
pentane
toluene
alcohols
2-butanol
2-propanol
carbonyls
2-propanone
3-methylbutanal
acetaldehyde
heptanal
hexanal
isobutyl aldehyde
pentanal
propanal
acids
ethyl acetate
ethyl butyrate
ethyl propionate
methyl acetate
others
dimethyl disulfide
formic acid ethyl ester
2-pentylfuran
total
a
IRH
FRH
control
0.01%
0.1%
0.2%
0.1%
0
460a
1254a
306a
4743a
42401a
428
1798
0b
0d
81ab
1677b
3885d
447
497
236b
449b
86ab
3069b
22698b
398
1859
873ab
208cd
210ab
3304b
11556c
257
2508
1178ab
301bc
250a
2179b
13435c
285
428
807
613
920
338
721
180
654
211
2504
682
2473
188
567
15592b
446d
9205c
1170a
88609a
168b
16890a
13470a
19825ab
187d
10345c
337b
7799c
0b
1872d
0d
15819b
1142bc
11196c
816ab
39969b
1152a
9994b
7096b
17757b
1907a
8888c
629b
14997c
641a
4188c
2578cd
23738ab
954c
15703b
724ab
25322c
281b
6640c
3878c
29896a
1364b
19466a
666b
16149c
1076a
4465cd
2578cd
2855
108
932
124
4863
229
1102
870
1041
284
0
0c
1983
148
0
0c
2323
99
0
1167bc
3728
127
0
1965bc
3126
384
206
2975b
7589
275
432
9868a
1964
81
114
526
1146a
0b
332bc
324b
0b
0c
1017a
236b
286bc
575ab
873ab
260bc
580ab
1178ab
562ab
941a
2038a
779a
144
340
113
78349cd
107934bc
111180bc
9423
199186a
52249d
120683b
Different letters (a−d) within a row are significantly different (P < 0.05), n ) 4.
0.2%
SEM
964
2038a
0d
0b
1443b
7397cd
629
566
340
65
57
458
1962
89
Rice Hull Extract on Turkey Meat Quality
J. Agric. Food Chem., Vol. 52, No. 2, 2004
377
Table 4. Volatiles Profile of Cooked Turkey Breast Meat with the Addition of Intact Rice Hull Extract (IRH) and Far-Infrared-Radiated Rice Hull
Extract (FRH) at 1 Daya
total ion counts × 104
sesamol
compound
hydrocarbons
1,1′-oxybisethane
1-heptene
2-octene
nonane
octane
pentane
toluene
alcohols
2-butanol
2-propanol
carbonyls
2,3-pentanedione
2-propanone
3-methylbutanal
acetaldehyde
heptanal
hexanal
isobutyl aldehyde
pentanal
propanal
acids
ethyl butyrate
ethyl propionate
ethyl acetate
methyl acetate
others
dimethyl disulfide
formic acid ethyl ester
2-pentyl furan
total
a
control
0.01%
0
661a
2462a
0
6246a
55161a
303
0
0c
158cd
0
1753c
8988c
0
IRH
FRH
0.1%
0.2%
0.1%
0.2%
SEM
0
303b
1656b
0
4240b
26703b
0
0
132bc
942c
742
3843b
22680b
137
969
48c
240cd
300
1609c
14923bc
289
553
0c
0d
45
1209c
7617c
183
455
65
232
99
427
3418
110
101
358
0
1588
0
2272
0
2144
166
1567
155
952
102
1469
373
26426ab
305de
16753
4067a
226269a
233c
37244a
36564a
0
28991ab
0e
18234
1293b
43804cd
569c
6852d
6394c
329
25592ab
2144b
21723
3015ab
132153b
2391b
27325b
19585b
66
36519a
3114a
21120
2643ab
81432c
4140a
17333c
11276bc
0
21734ab
619cd
16469
908b
73389c
428c
11597cd
10933bc
0
17551b
866c
16993
395b
23761d
312c
4375d
4096c
104
4085
146
1931
631
13541
388
2518
2416
685a
0b
0
0d
202b
0b
0
0d
566a
0b
0
2484c
543a
0b
1007
4143ab
127b
362a
4587
3036bc
279b
322a
6160
5174a
70
74
1507
411
1388a
1381
1906a
444c
1629
0b
884bc
2031
1855a
1101ab
1726
1973a
495c
1438
272b
425tagnc
1935
155b
115
270
269
420020a
121588d
93985d
23525
277130b
218353bc
165886cd
Different letters (a−d) within a row are significantly different (P < 0.05), n ) 4.
effect of antioxidants has been reported (19, 20). Thus, the high
a values in IRH- and FRH-added treatments can also be
explained by their antioxidant effect as well as the original
browning color of extracts.
Inhibition of Off-Odor Volatiles. The production of warmedover flavor is the most critical problem, and the role of
antioxidants is important in storing precooked meat. Rice hull
extracts reduced effectively the off-odor volatiles in cooked
turkey breast but produced newly a few volatiles that are
supposed to be responsible for the characteristic rice hull odor
(Table 3). Considerable amounts of total volatiles were reduced
by the addition of rice hull extracts (both IRH and FRH), but
they were higher than that of the sesamol treatment. When
volatile compounds related with lipid oxidation were compared,
volatile aldehydes (propanal, pentanal, hexanal, and heptanal)
and hydrocarbons (pentane, octane, and nonane) were significantly decreased by the addition of rice hull extracts. Hexanal
was the most predominant volatile compound in the control
meat, taking up almost 50% of the total volatiles, and it was
reduced to only 17-18% of the control by the addition of rice
hull extracts at a 0.2% level. In general cases of cooked meat,
the amount of hexanal was the most correlated with the TBARS
value (21, 22), and it can be a good indicator.
Although there was little difference of total volatiles between
IRH and FRH treatments, the volatiles compositions were
somewhat different. At the level of 0.1% addition, a lower level
of volatile aldehydes was found in FRH-treated turkey meat,
showing that the antioxidant activity of FRH was greater than
that of IRH. However, FRH treatments had some peculiar
volatiles, such as formic acid ethyl ester and methyl acetate,
which might be responsible for the characteristic rice hull odor.
This result showed that FIR radiation increased not only the
antioxidant properties of rice hull extract but also the special
rice hull odor. The effects of rice hull extracts on volatile
compounds were concentration-dependent, and the effect of
reducing aldehydes was much more distinct when both IRH
and FRH were added at the level of 0.2% than when they were
added at 0.1%. When the antioxidant effect of sesamol was
compared in terms of hexanal content, only 9% of hexanal was
present in sesamol-treated turkey breast compared with the
control. Thus, the hexanal-inhibiting activity of pure sesamol
at the level of 0.01% was ∼2 times higher than that of IRH
and FRH at 0.1-0.2% at the beginning storage. This can be
attributed to the difference of their antioxidant phenolic contents.
The antioxidant properties of FRH were more distinct after
1 day of aerobic storage of precooked turkey breast (Table 4).
Despite the short period of storage (only 1 day), a considerable
degree of lipid oxidation proceeded and large amounts of volatile
aldehydes increased at all treatments. About 2.5 times higher
amount of hexanal was found in the control meat compared
with the beginning of storage. Sesamol at 0.01% showed still
strong antioxidant effects, and an even more interesting finding
was that 0.2% FRH treatment had antioxidant activities as strong
as those of sesamol. The amounts of all volatile aldehydes in
0.2% FRH were statistically almost the same or less than the
sesamol treatment. Therefore, the effects of FIR and added
concentration of rice hull extracts were very clear after 1 day
of aerobic storage. However, rice hull extract-treated samples
378
J. Agric. Food Chem., Vol. 52, No. 2, 2004
Nam et al.
Table 5. Volatiles Profile of Cooked Turkey Breast Meat with the the Addition of Intact Rice Hull Extract (IRH) and Far-Infrared-Radiated Rice Hull
Extract (FRH) at 3 Daysa
total ion counts × 104
sesamol
compound
hydrocarbons
1,1′-oxybisethane
1-heptene
2-octene
octane
pentane
toluene
alcohols
2-butanol
2-propanol
carbonyls
2,3-pentanedione
2-propanone
3-methylbutanal
acetaldehyde
heptanal
hexanal
isobutyl aldehyde
pentanal
propanal
acids
ethyl acetate
ethyl butyrate
ethyl propionate
methyl acetate
others
dimethyl disulfide
formic acid ethyl ester
2-pentylfuran
total
a
control
0.01%
0
553a
2906a
7351a
47921a
503ab
IRH
FRH
0.1%
0.2%
0.1%
0.2%
SEM
440
53b
504d
1645d
7748c
447ab
0
515a
2774a
7808a
48704a
418b
0
681a
1247bc
5391c
38614a
512ab
0
320ab
1587b
4024b
28826b
510ab
0
0b
846cd
2167c
11611c
678a
179
103
161
535
3011
54
0b
1921
236b
2497
93b
1664
123b
920
243b
647
609a
1121
102
432
543
15892
293d
15120b
3586
247075a
191c
41385a
45531a
58
20698
285d
23237a
1668
72834e
989b
11991c
11432c
575
14725
1406b
27027a
3364
223960ab
1500ab
42193a
37261ab
0b
214
0b
0d
397b
90
0b
0d
819b
0
0b
1113c
2269ab
0
0b
1401c
805b
1115b
235
503b
1083b
140
1452a
1452b
668
433147a
158961d
419502a
687
17561
2101a
27267a
3450
200817b
2050a
40052a
28819b
427
16044
945c
25118a
3193
159509c
1471ab
26717b
26478b
332
22651
1169bc
27944a
1885
114317d
1449ab
15207c
14601c
144
2458
109
1747
469
11568
162
2186
3090
2500ab
176
0b
2151b
6345a
107
523a
5026a
1149
91
22
212
1336a
1712b
1200
852b
1599b
1144
676b
2982a
646
126
227
296
313160b
304485b
232898c
18405
Different letters (a−d) within a row are significantly different (P < 0.05), n ) 4.
had still characteristic volatiles, and ethyl propionate was newly
detected at the FRH treatments.
At 3 days, antioxidant effects were mainly found in the 0.01%
sesamol and 0.2% FRH treatments (Table 5). In the case of
the control meat, the amount of volatiles did not much increase
between 1 and 3 days of storage. On the other hand, treatments
with rice hull extracts had largely increased amounts of lipid
oxidation product volatiles. The antioxidant properties of rice
hull extracts did not last as long as those of sesamol did. This
result can be attributed to the relatively low concentration of
the phenolic compounds in rice hull extracts compared to the
pure sesamol. Nevertheless, FRH treatments showed still more
antioxidant activities than the IRH, and added concentration was
a critical factor in inhibiting off-odor volatiles. Various volatiles
responsible for the characteristic rice hull odor (formic acid ethyl
ester, methyl acetate, ethyl acetate, and ethyl propionate) were
mainly found at 0.2% FRH treatment at 3 days.
Conclusions. Reduced lipid oxidation products in cooked
turkey breast verified the antioxidant properties of rice hull
extracts, and FIR radiation could increase significantly the
antioxidant activities. Turkey meat treated by rice hull extracts,
however, had some problems in the increased brown color and
the generation of characteristic rice hull odor. To increase the
availability of rice hull extracts as a food additive, more efficient
ways to increase the antioxidant activities are needed by
concentrating more antioxidant components and/or excluding
the unnecessary portions. This study showed a good method to
increase the antioxidant activities of rice hull extract using FIR
radiation. Consequently, rice hull extract will be an excellent
natural and cheap antioxidant source.
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Received for review September 27, 2003. Revised manuscript received
November 28, 2003. Accepted December 3, 2003. This study was
supported by the Ministry of Science and Technology (MOST) and the
Korea Science and Engineering Foundation (KOSEF) through the
Coastal Resource and Environmental Research Center (CRERC) at
Kyungnam University (R12-1999-025-08003-0), Korea, and State of
Iowa funds. J.-H.K. received a scholarship from the BK21 Program of
the Korean Ministry of Education.
JF035103Q